1. Field of the Invention
The present invention pertains to methods and devices for performing fine needle aspiration biopsies and large core biopsies. In particular, the present invention relates to fine needle aspiration and large core biopsy devices having enhanced cell and/or tissue collection features and to improved cell and/or tissue collection methods.
2. Description of the Related Art
To diagnose suspicious palpable or non-palpable masses in soft tissues, such as breast tissue, often requires that a sample thereof be obtained. Currently available cell and tissue extraction techniques include fine needle aspiration and large core techniques.
Fine needle aspiration (hereafter FNA) is a process wherein a 20 to 25 gauge needle attached to a syringe is inserted through the skin to the target lesion. While pulling back on the syringe plunger to create a vacuum, the needle is moved back and forth at least 5 to 10 times in a translational and rotational movement, targeting multiple sites within the lesion. The movement of the needle within the target lesion, as well as the applied suction, hopefully causes cells within the lesion to be dislodged and forced into the internal lumen of the needle. The needle may then be retracted from the tissue. The collected cells may then mounted on slides and examined by a cytopathologist for possible malignancy.
Core biopsy techniques, on the other hand, utilize a larger gauge needle, typically 14 to 18-gauge. Whereas FNA techniques generally collect only individual cells, core biopsy devices and techniques collect a much larger sample and generally preserve the tissue architecture. In core biopsy, the most popular means for retrieving a core sample utilizes a spring-loaded, hand held automated gun is used to retrieve the sample. The gun includes an inner needle having a tissue-receiving slot and an outer cutting needle surrounding the inner needle, both spring loaded. When the gun trigger is depressed, the inner needle is shot through the soft tissue to a predetermined distance, generally referred to as the "throw" of the gun. The inner needle includes a slot on the side thereof that is designed to receive the tissue to be severed. Immediately after the tissue enters the tissue-receiving slot, the outer needle is released, severing the tissue and leaving a tissue core inside the slot of the inner needle. The assembly is then retracted and the core specimen sent for histopathological analysis.
Both FNA and core biopsy devices, however, suffer from a number of disadvantages. Turning first to fine needle aspiration, the success rate of FNA procedures appears to be heavily dependent upon the skill and degree of experience of the operator. Indeed, at least 30% of FNA procedures performed on breast tissue yield inadequate or non-diagnostic cell samples. Non-diagnostic samples are those in which, for example, no cells are present in the material extracted from the breast, those in which only fat cells are retrieved or those in which an insufficient number of breast epithelial cells are present for the cytopathologist to adequately characterize the retrieved sample. Failure to retrieve a diagnostic quality sample does not alleviate the need for a positive diagnosis, however; and in those instances in which FNA fails to return a proper sample, the procedure must be repeated. Alternatively, a more invasive procedure must be performed to retrieve the desired sample. Moreover, the translational movement of the FNA needle, repeated at least 5 to 10 times, may be painful to the patient and traumatic to the tissue mass within which the biopsy is performed. FNA, for at least these reasons, can prove to be a frustrating procedure to an inexperienced physician, who may, therefore, opt to carry out the relatively more invasive core biopsy procedure.
Large core biopsy techniques and devices have enjoyed a comparatively greater acceptance than have FNA devices and techniques. Core biopsy needles are typically about 14 gauge, are typically shot into the target lesion under great acceleration, and retrieve a comparatively larger amount of tissue than do FNA needles. Because of the large gauge of the needles and the high acceleration under which they are introduced into the mass to be biopsied, the procedure is more invasive, painful and psychologically traumatic. Moreover, it is often necessary to repeat the procedure four to six times to obtain an adequate specimen, whether the biopsy is carried out under stereotactic, ultrasound or manual guidance. Additionally, there are instances in which the needle may not penetrate and may even bounce off particularly dense tissue. The procedure, therefore, is often a painful and frightful experience for the patient. Indeed, the loud report of the automatic biopsy gun (often compared to that of a large staple gun) as the trigger is depressed and the needle is fired invariably makes the patient (and sometimes the physician) flinch or startle, which may cause the needle to miss its target.
Other problems occasionally encountered with core biopsy techniques include failure of the outer cutting needle to completely advance over the inner needle, due to highly dense tissue. Removal of the device may then be difficult, as compressed tissue may have entered into the slot in the inner needle without being completely severed from the mass. Removal of the device in such cases may lead to significant hematomas, swelling and damage to collateral tissue. Moreover, core biopsy techniques may be contraindicated in cases wherein augmentation prostheses are present in the breast.
Safety is also a concern with conventional FNA and core biopsy techniques, as the thrusting motion inherent in FNA procedures and the high needle accelerations of core biopsy procedures can lead to accidental puncture wounds to the patient or the surgeon. Such accidental puncture wounds increase the possibility of accidental contact with harmful viruses, such as the HIV or hepatitis B virus. Moreover, such thrusting motion and/or high acceleration may lead to a bending of conventional cannulas and/or stylets, particularly when dense tissue is present. Such bending may injure the patient and may be a contributing factor in the relatively high failure rate of FNA and related biopsy procedures.
What are needed, therefore, are improved cell and tissue collection methods and devices that would allow a safe and consistent collection of diagnostic quality specimens. Indeed, although FNA biopsy techniques have somewhat fallen into disfavor, primarily due to their poor success rate, FNA remains the least invasive technique for rapidly screening soft tissue, such as breast tissue, for malignancies. There has been a long felt need, therefore, to more consistently obtain diagnostic quality biopsy specimens, using minimally invasive and thus minimally traumatic means and techniques. What are also needed are cell and tissue collection methods and devices that are not as dependent upon the skill of the operator as are FNA biopsy techniques. Moreover, practitioners and patients alike have long felt the need for cell and tissue collection methods and devices that are less traumatic to surrounding soft tissue and that result in fewer complications, such as bruising and swelling. There has also been a long felt need for diagnostically effective alternatives to automatic core biopsy guns, alternatives that preferably do not depend upon the violent release of spring loaded needles.